Step controlled tube expander

ABSTRACT

A power operated tube expander apparatus having automatic step control for deep hole rolling of a tube to a header sheet. A stop collar in the form of a thrust assembly is supported on the cage behind the expander rollers to prevent movement of the cage inward of the tube during the expansion operation. After rolling a longitudinal segment of tube, controls are operable to displaceably step the collar a predetermined incremental distance longitudinally away from the expander end. This allows an additional segment of tube to be subsequently rolled. Stepping of the collar continues until completing total joinder of the tube to the header.

United States Patent 1 Martin l [4 1 Dec. 17, 1974 STEP CONTROLLED TUBE EXPANDER Paul Warren Martin, Springfield, Ohio [75] Inventor:

[52] US. Cl 72/122, 72/125, 29/202 D [51] Int. Cl..... B2ld 39/06 [58] Field of Search 72/20, 122, 125-, 29/202 D [56] g References Cited 7 UNITED STATES PATENTS 1,089,170 3/1914 Wiedeke 72/122 l,798,442 3/1931 Wiedeke 72/122 2,767,766 10/1956 Mathews 72/122 2,854,058 9/1958 Baker 72/l22 3,683,48l 8/l972 Blackburn et al. 3,718,017 2/l973 Blackburn 2 /202 Primary ExaminerLowell A Larson Attorney, Agent, or Firm-Daniel Rubin 57 ABSTRACT A power operated tube expander apparatus having automatic step control for deep hole rolling of a tube to a header sheet. A stop collar in the form of a thrust assembly is supported on the cage behind the expander rollers to prevent movement of the cage inward of the tube during the expansion operation. After rolling a longitudinal segment of tube, controls are operable to displaceably step the collar a predetermined incremental distance longitudinally away from the expan der end. This allows an additional segment of tube to be subsequently rolled. Stepping of the collar continues until completing total joinder of the tube to the header.

10 Claims, 13 Drawing Figures PMENTLME 1 H974 SHEH 25E 7 1 STEP CONTROLLED TUBE EXPANDER BACKGROUND OF THE INVENTION 1. The field of art to which the invention pertains generally comprises the art of metal deforming and more particularly to tube expanders of the roller and mandrel type for joining tubes into tube sheets.

2. Tube expande'rs are widely used by manufacturers of heat exchangers or the like for joining tube ends to headers and are available from a variety of commercial sources. In their usual construction, the roller and mandrel type tube expander is comprised of a tubular cage with slots in its periphery containing rollers lying at an oblique angle to the cage axis. A rotatable tapered mandrel extends axially through the cage in driving contact with the rollers for rotating the rollers while forcing them operably outward against a tube wall thereat to roll expand the tube against the header.

For certain applications such a'sin atomic steam generators, high pressure feed water heaters etc., the tube, sheet or header is frequently of very thick cross-section enabling it to withstand a tendency to bow under pressure. To insure proper joinder of the tube to the header for those applications, it has been found preferableto roll the tube the entire axial depth of thehea'der sheet. Because of the large amount of metal to be deformed, deep hole rolling is usually performed in sequential steps along the tube length. Positioning the expander for each step or-segment of tube is a thrust or stop col-- lar engageable with the tube endor header face to prevent advance of theexpander inward of the tube during the course of the rolling operation. As each, segment is completed, the thrust collar is manually displaced fur-. ther from the rollers for expanding the; next subsequent incremental segmentof' tube. By this-means, rolling uniformity has been reasonably obtained throughout controlled operation over; the entire expandable; length of tube. I

SUMMARY OF THE INVENTION The invention relates to tube expanders and more particularly to apparatushaving; automatic steptrolling controlfor deep hole rolling of a,tube-toaheaderfsheet.

This is achievedyinaccordance herewith. byjmeansof;

apparatus. that includes pneumatic control circuitry which is operative following completion of eachrolling cycle to automatically relocate the thrust; collar in preparation for the next rolling cycle.

A stop collar in the form of-a thrust assembly is, sup-1 ported on the expandercageandisoperably connected to an elong'atedstepping;bar. A latching mechanism is longitudinally movablejoverthe stepping bar; and-in conjunction with a pneumatic stepping cylinder-isopen able concomitantly. therewith in controlled sequence to displace the stepping bar and collar increasingly, rearward after each rolling cycle. The extent of displacement corresponds to the next incremental segment of tube to be rolled. In this manner, stepping reliability is both assured'and substantially simplified for obtaining high quality joint formation without the inaccuracies, unreliability and tedious procedures associated with such similar purpose devices of the prior art.

It is, therefore, an object of the invention to provide a novel step controlled tube expander for deep hole BRIEF DESCRIPTION OF TI -IE DRAWINGS FIGS, 1 and 2 are a plan and'side views, respectively,

' of a single spindle expander operative in accordance ulationof the;tooljwhile antejye hook 20 providesfor- I herewith;

FIGS.'3and,4 are a plan and side views, respectively, .of a multirspindle expanderoperative inaccordance herewith;

FIG. 5 is, an enlargedv plan. view of. the stop collar thrust assembly of the single spindleunit;

FIG. 6 is a, side elevation of the thrust'assemblyof FIGS; J

FIG. 7 is an, enlarged plan view of the stop collar thrust; assembly of the multi-spindle unit;

FIG. 8. is a sectional elevation. 'takensubstantially along the lines, 88; of FIG. 7; I

FIG; 9. is a, sectional. elevation through a typical sto collar; thrust assembly in accordance herewith;

FIG. 10 ;is a fragmentary elevation, of the encircled portion, 1K0 of, FIG! 9 illustrating component, relationship during thecourse of'displacing the stop collar;

FIG. 11; is asectionalelevation through the latching mechanism'hereof; and 7 FIGS. 1-2 and: 1 3," are diagrammaticqcircuit arrangementsof pneumatic controls. for thesingle spindle and muIti-spindle units, respectively,.

Referring now to the. drawings and'particularly'to FIGS. 1-4, thereare illustrated both single andfdual spindle; power fedi'tube expander units designated; 1 0 and-11 0f a}.typ e generally. available. in theprior art and: modified in; accordance. with; .theinvention-hereof. Each. spindle unit is comprised; ofian; outer casing 13,.

housing. the various operatingcomponents. to which pressurizedair fromla; suitable; source is furnished via. a supply. hose, l5}. and dissipated; through an exhaust hose 16'. Gripping; handles. 18 and 19 on the back and;

receipt; ofia. suitable balancer for balanced support of thCgIOOl inQpeIflIIYQpOSiIIQm Assoeiatedwithdual:unit 1111. are a, pair 'of. transversely, extending,- adjustment serews-22;,andr=2 3j afiordingspanspacingbetween units to,be accurately -pre-setin correspondence with tube spacing to be encounteredzForward'of each-unit isa frame 2.5 on the; nderside of which, is. secured a. base 26 supporting; the, cantilevered; expander; end. of; the

tool.

Extending forward through. base; 26; is the expander. cage-27 for Whichreference is alsozmade toF-IGS. 5--7.

and 9. The cage is of elongated tubular construction formed with a plurality of semi-spherical recesses 28 periodically spaced along its longitudinal length. Supported on the cage is a stop collar thrust assembly 29 while extending internally through the cage is a tapered mandrel 30 adapted to be driven by an air motor not shown. At the forward or expander end of the cage are three or more cylindrical forming rollers 33 circumferentially displaced in the cage periphery and skewed obliquely to the axis thereof. The rollers are supported on mandrel 30 to be rotatably driven thereby in a well known manner for expanding a tube 31 radially outward against a header 32. Also supported from frame 25 are a step cylinder 35 and a latch assembly 36 to be described below and through which extends a stepping in its periphery correlated to the stepping displacement of collar to be effected.

Comprising the stop collar thrust assembly, which is most completely shown in FIG. 9, are a plurality of tandem arranged components supported about the periphery of cage 27. At the front of the assembly is a start collar 40 having a front face 42 adapted for engagement against theface of a tube header 32 and an enlarged rear flange'41 adapted for operating a start valve 108as will be understood. Internally rearward from front face 42 the collar is bored at 44 to form a radial flange 45-adapted to abut the end of tube 31. Immediately behind flange 45 the collar is counterbored at 46 for receiving an adjustable sleeve 49. Through a slot 47, an adjustment screw 48 connects to sleeve 49 which is threaded about its periphery at 56 whereby it can be adjustably positioned in internal thread 59 of thrust collar 60. A,.set screw 61 secures the position between sleeve 49and collar 60. Sleeve 49 at its terminal end turns inwardly forming a radial flange 52 to enclose coil spring 53 compressed therein against the end flange of a ny-lonsleeve 55. Latter sleeve 55 surrounds cage 27 in extending to inward of tube 31 for preventing cage drag against the tube surface in the course of expansion as might otherwise occur. 7

Thrust collar contains thrust bearing 64- secured by means of a nut 65 which in turn m'aintainsthe assembled relation of components via a retainer ring 66 positioned in collar groove 67. Secured to the thrust collar by means of a set screw 68 is a thrust bracket 69 extending transversely thereto. Positioned immediately tending release bracket 83. Secured to andextending through the release bracket is the threaded outboard end of the, stepping bars 38 which slideably terminate through an aperture 84 in parallel thrust bracket 69. With the single spindle units, a guide bar 88 is connected to release bracket 83 similarly as stepping bar 38 in order to balance and absorb the applied longitudinal and rotational forces. An adjustment screw enables setting of proper spacing between brackets .to maintain stepping bar position relative to the operation of latch assembly 36 as will be understood.

For withdrawing the stop collar thrust assembly following rolling completion of each incremental tube segment, there is provided control apparatus that includes a stepping cylinder 35 operative concomitantly and in conjunction with latching mechanism 36. The

stepping cylinder is of a commercially available type,

sentially elongated body 92 having a longitudinally central aperture 93 containing a double'acting'displace- I able piston member 94. A transverse body aperture 95 lease collar includes a radially inward flange 78 operaaccommodates stepping bar 38' extending therethrough. Piston '94 is double flanged at each end forsupporting an intervening O-ring seal 97 and likewise accommodates stepping bar 38 by meansrof a central oval-like aperture 98 aligned generally superposed with body aperture 95. Formed internally at the underside of piston aperture 98 is a radial tongue or finger 99 for engagement with stepping bar recess 39 in controlled sequence to latch or release the bar. Pneumatic fittings 100 and. 101 communicate with opposite ends of the 'piston for effecting its controlled operation.

the diagrammatic illustration of pneumatic control components shown in FIG. 12. Placing main valve 103 in the ON position supplies operating air to tube rolling motor 104 and through the'motor to one chamber of a dual chamber sump 105. From the sump, air is supplied to start valve 108, four-way .valve 109 (fourth port plugged) and to emergency stop valve 110. At the same time, four-way valve 112 is energized forsupplying air to the left endof cylinder 111 and to pilot 113 which acts to close valve 114. A pin 119 on the operating rod of cylinder 1.11 operates valve 124 to openposition. Concurrently, flow control valve 116 is energized for supplying air to the left end of stepping cylinder 35 maintaining it in retracted position and through fourway valve 118, latch assembly36 is energized forcing piston 94 upward for tongue 99 to engage stepping bar recess 39 securing the bar in latched position. Depressing pushbutton l22-temporarily on four-way valve 118 transfers air pressure from latch fitting 101 to latch fit ting 100. This releases stepping bar 38 from its latched relation permitting stop collar thrust assembly 29 to be positioned at the expander end ready to begin rolling operation for the first segment of tube.

To initiate the rolling cycle, the expander end is placed into the end of tube 31 until start collar contacts either the tube end or the header sheet 32 forcing the collar backward over sleeve 49 sufficient to operate start valve 108. (See also FIGS. 6 and 9). With start valve 108 in open position, air is supplied through motor .104 is fully operative through shuttle valve 130 and regulator 131 for supplying reduced pressure air to valve 132 to pilot 133 and rendering four-way valve 112 operable. When the latter occurs, air is supplied to flow control valve 134 which simultaneously supplies air to the right endof cylinder 111 and through flow control valve 135' to the right end of stepping cylinder 35.,Concomitantl'y, air is supplied through shuttle valve 138 to latch 36 placing it in unlatched relation enabling .the energized stepping cylinder to relocate the latch assembly leftward the equivalent of a step on bar 38 to about-line 137 (FIGS. -6).

While the latter is occurring, pilot 139 is energized to operate four-way valve 1 18 previously set manually. With valve 1 18 operating it allows an air bleed from the left end of cylinder 111 to atmosphere and from pilot 113 to open valve 114 while venting latch 36 and the left end of stepping cylinder 35. Air entering the right end of cylinder 111 induces push to be applied to the handle of motor 104 causing it to operate in the forward direction. With the motor operating, its right air line is pressurized via sump 105 and valve 114 through shuttle valve 130 and pressure regulator 131. Reduced pressure from the regulator is supplied through valve 132 to pilot 133 holding valve 112 in its operative position, while pressure regulating valve 140 through shuttle valve 141 and pilot 142 operates valve 145. Returning valve 145 to its normal relation effects a bleed of air pressure from pilot 126; etc., thereby eliminating the self holding circuit previously instituted. Air pres sure will hold valve 112 operative until motor 104 completes the rolling operation, at which time the motor is de-energized by a torque control, not shown.

On encountering a predetermined torque level as set by the torque control, motor operation in a forward direction is discontinued, permitting pressure at the right end of motor 104 to decrease to near zero. This allows pilots 133 and 142, along with their respective valves 112 and 145, to assume their normal positions. Valve 112 is then enabled to exhaust air from the right end of stepping cylinder 35 and through various intermediate components from fitting 100 oflatc h mechanism 36. At the same time, air is supplied to pilot 113 for closing valve 114 and to the left end of'cylinder 1 1 l for pulling on the motor control handle and causing the motor to operate in a reverse direction for withdrawing mandrel 30. Likewise energized at that time are valve 118 and latch fitting 101 to move latch tongue 99 into its latch relation with stepping bar .38 while through flow valve 116, the left end of stepping cylinder 35 is energized.

. The effect of the latter is to draw stepping bar 38 backward forcing bracket 83 against release collar 71 to obtain release thereof by uncoupling it from cage 27 and allowing thrust assembly 29 to be moved back a distance corresponding to the separation spacing of cage recesses 28. r I g The foregoing continues repetitively until completing I the final rolling step at which time valve 123 is operative by a pin 121 extending laterally from the stepping bar behind collar flange 83. This thereby prevents the start of additional rolling cycles until the thrust assembly has been forwardly repositioned to initiate a rolling operation for a subsequent tube. In the event of an emergency, manually pressing the button. on valve 110 allows air to energize pilot 1 46 energizing pilots 146 and 142 to close their respective valves. This, in turn, bleeds air from pilot 133 allowing valve 112 to return tion, the self holding circuit is'discontinued if not al ready discontinued as-above. Valve 114 prevents false starts of air motor 104.

Operation of the dual unit will not be described with particular reference to FIG. 13. With main valves 205 and 206 in the ON position, air is supplied to each of the rolling motors 207 and 208, respectively. Air from the motors via shuttle valve 210 is supplied to one chamber of sump 211 to in turn supply manifold 212. This'energizes start valve 108 and four-way valve 213, while at the same time air is being applied to emergency stop valve 216 and through four-way valve 217 and manifold'218 to energize the left end of air cylinders 223 and 224 and to pilots 219 and 220. This closes valve 228 while air is passed through four-way valve 225 and flow controlvalve 226 to the right end of stepping cylinder 35. Air is also passed through four-way valve 227 to the latch side of latching assembly 36 un- I less valve 227 has been manually operated. Depressing thrust assembly can be positioned toward the expander in preparation for first step rolling in a pair of parallel tubes 31. Pins 229 and 230 onthe operating rods of cylinder 223 and 224 operate valves 231 and 232 to open position.

Positioning the expanders inward of the tube ends as before and pushing forward on the unit triggers start valve 108. This serves to supply air'through valves 231,

232 and 233 and shuttle valve 234 to pilot valve 235 for operating four-way valve 213. With the latter enerv gized, air is passed through valve 240 andshuttle valve 234 back to pilot.235, thus forming a self-holding circuit enabling the motor to become fully operative. Air is thereby allowed to flow through shuttle valve 241 to pressure regulator 242and through valve 243 to pilot 244. With pilot 244 energized, four-way valve 217 supplies air to pilot 248 and flow control valves 249 and 250 feeding toggle valves 251 and 252, respectively. These in turn supply the right end of air cylinders 223 and 224 while-valve 217 effectively bleeds pilots 219 and 220 and the opposite end of the cylinders 223 and 224 through manifold 218. Pilot 248 being energized, will operate valve 225 allowing air to flow through shuttle valve 256 to place latch assembly 36 in unlatched position while also passing air through-com trol valve 257 to pilot 258 for operating four-way valve 227 and to the left end of stepping cylinder 35. As before, this enables the energized stepping cylinder to relocate the latch assembly leftward over bar 38 to about line 137. At thesame time, air is being bled through valve 225 to atmosphere from control valve 226 and the right end of stepping cylinder 35 and through the four-way valve 227 from the latching side of the latch assembly 36. With energizing the right end of air cylinders 223 and 224 control handles of air motors 207 and 208, respectively, are pushed causingthe motors to run in a forward direction.

So long as the motors operateforwardly, the air lines from their right ends are pressurized supplying shuttle valve 259, sump 21l,valves 228 and: 241, regulating valve 242and valve 243 to pilot-244. The latter places four-way valve 217 in operative position while pilot 263 is energized through flow control valve 264 and shuttle valve 265 toclose valve 240. Pilot 235 is then bled eliminating the self-holding circuit previously dc scribed. This relation of active components continues until the preset torque level is encountered at which time the motors are de-energized by the torque control, not shown.

When the motors are stopped, air pressure at their right ends nears zero allowing pilots 244 and 263 and their respective operative valves 217 and 240 to resume their normal position. As the operative position of valve 217 is transferred, it will exhaust the right end of cylinders 223 and 224 and pilot valve 248 via the'intervening toggle and control valves 249-252. Transfer likewise applies air pressure through manifold 218 to pilots 219 and 220 for energizing the left side of air cylinders 223 and 224 to initiate reverse operation of motors 207 and 208. Pilot'220 will cause valve 228 to close whereas the effect ofpilot 219 is to switch valve 225 to an air bleed position through control valve 257 from the left end of stepping cylinder 35 and via pilot 258 and shuttle valve 256, from the unlatching side of latching assembly 36. Simultaneously with transfer, valve 225 will apply air pressure through valve 227 to the latching side of latch assembly 36 while air through valve 226 will apply air to the right side of stepping cylinder 35. The effect of the latter is to draw stepping bar 38 backward forcing bracket 83 against release collar 71 to obtain release or uncoupling thereof and allowing stop thrust assembly 29 to be moved one step back on the expander cage asbefore.

The foregoing continues repetitively until completing the final rolling step at which time valve 233 is operated by pin 121 thereby preventing a start of additional cycles unitl after the thrust assemblies have been forwa'rdly repositioned. Valves 231 and 232 are each operated by one of motors 207 or 208 when the motors are in their home position thereby likewise preventing any starting cycle until after the-previous cycle has been completed. The unit is then ready to repeat the total cycle for another tube.

Valve 216 functions as an emergency stop which when manually depressed allows air to flow to pilot 266 for closing valves '243 and 240 which in turn bleed air from pilot 244 allowing valve 217 to return to its normal position. With valve 240 in closed relation, the selfholding circuit is dropped out if not already eliminated asabove. Valve 228 functions as' a safeguard against false starts of the air motors. Toggle valves 251 and 252 enable operation of one motor without the other. A fm-. ger latch 268 which when pivoted upwardly in the posi-- tion shown in FIG. 8 permits manual reset of the thrust assembly after completion ofthe last operating cycle.

By the above description, there has been disclosed novel expander apparatus capable of controlled step v rolling for deep hole rolling of a tube to a header sheet.

A stop collar thrust assembly is supported behind the expander rollers in the direction of advance to inward of the tube and operation is initiated with the stop collar in the forwardmost position bearing against the tube end or header sheet. In this position pneumatic circuitry is triggered via start switch 108 for operating the motor in the. forward moderSimultaneously, latch assembly 36 is detached from stepping bar 38 while step cylinder 35 moves the latch assembly to a forward position about the bar. Upon completing each rolling cycle for each incremental segment of tube, the motor is automatically stopped by a torque control at which time the latch assembly 36 is operative to latch onto stepping bar 38. In seriatim, the stepping cylinder 35 then draws the bar and thrust assembly backward as a unit a one step distance of the bar to prepare the tool for the next operating cycle.

To begin operation again, it is only necessary that the operator again force the stop collar against the tube or header to initiate the next rolling step. Alternatively,

- the entire tool can be biased toward the tube to eliminate operator intervention between steps. By this means, all rolling steps are insured and accidental step omission is precluded. After the last step has been rolled, the stepping bar actuates a cycle completion valve 233 thereby preventing the machine from rerolling the last step. Other safety features have been provided although not specifically mentioned. The entire unit is thereby rendered self-contained and is readily adaptable to either a single or a multiple unit device for rolling one or more tubes simultaneously. By this means, the previous difficulties and psychological factors associated with deep hole rolling are diminished or eliminated as to substantially reduce thehigh labor costs previously associated therewith.

Since many changes could be made in the above construction and many apparently widely different embodiments of this inventioncould be made without departing from the scope thereof, it is intended that all matter contained in the drawings and specification shall be interpreted as illustrative and not ina limiting sense.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: I

tion:

a. a rotatable expander for insertion into an end of a receiving tube to be expanded against a header sheet;

b. motor means for rotatably driving said expander within the receiving tube in rolling relation'to a longitudinal wall segment thereof for effecting tube expansion of the segment against the header;

c. a stop collar supp'orted on said expander' at a location outward of the receiving tube end to prevent said expander from advancing inward of the tube beyondsaid segment while said rolling relation-is being conducted; and i d. control means operable after said expansion is completed to displaceably step said collar to a support location a predetermined distance away from the tube end for'said expander to subsequently conduct expansion on an additional wall segment of said tube.

2. Tube expander apparatus according to claim 1 in which said control means is pneumatically actuated.

3. Tube expander apparatus according to claim 2 including latch means and a stepping cylinder concomitantly operative for displaceablystepping said collar.

4. Tube expander apparatus according to claim 1 including coupling means operatively effective while said rolling relation is being conducted to longitudinally couple said collar to said expander and said control means includes release means effective when operable to release said coupling means for displaceably stepping said collar. 5. Tube expander apparatus according to claim 4 including a longitudinally movable stepping bar operably 1. Tube expander apparatus comprising in combinaconnecting said collar to said control means, said stepping bar having a plurality of recesses defined longitudinally spaced apart in its periphery at incremental distances correlated to the stepping distances to be ef' fected by said control means.

6. Tube expander apparatus according to claim including latch means operable in controlled sequence by said control means to a latch or release relation with said stepping bar.

7. Tube expander apparatus according to claim 6 in which said expander comprises an elongated cylindrical cage having a plurality of annular recesses defined longitudinally spaced apart in its periphery at distances corresponding to the incremental recess distance of said stepping bar, said collar is supported on said cage and said coupling means is operatively cooperative with said recesses to longitudinally couple said collar to said expander.

8. Tube expander apparatus according to claim 6 including stepping means operable in controlled sequence by said control means to displace said latch means in a first direction relative to said stepping bar when the latch means is in a release relation therewith which said control means is pneumatically actuated. 

1. Tube expander apparatus comprising in combination: a. a rotatable expander for insertion into an end of a receiving tube to be expanded against a header sheet; b. motor means for rotatably driving said expander within the receiving tube in rolling relation to a longitudinal wall segment thereof for effecting tube expansion of the segment against the header; c. a stop collar supported on said expander at a location outward of the receiving tube end to prevent said expander from advancing inward of the tube beyond said segment while said rolling relation is being conducted; and d. control means operable after said expansion is completed to displaceably step said collar to a support location a predetermined distance away from the tube end for said expander to subsequently conduct expansion on an additional wall segment of said tube.
 2. Tube expander apparatus according to claim 1 in which said control means is pneumatically actuated.
 3. Tube expander apparatus according to claim 2 including latch means and a stepping cylinder concomitantly operative for displaceably stepping said collar.
 4. Tube expander apparatus according to claim 1 including coupling means operatively effective while said rolling relation is being conducted to longitudinally couple said collar to said expander and said control means includes release means effective when operable to release said coupling means for displaceably stepping said collar.
 5. Tube expander apparatus according to claim 4 including a longitudinally movable stepping bar operably connecting said collar to said control means, said stepping bar having a plurality of recesses defined longitudinally spaced apart in its periphery at incremental distances correlated to the stepping distances to be effected by said control means.
 6. Tube expander apparatus according to claim 5 including latch means operable in controlled sequence by said control means to a latch or release relation with said stepping bar.
 7. Tube expander apparatus according to claim 6 in which said expander comprises an elongated cylindrical cage having a plurality of annular recesses defined longitudinally spaced apart in its periphery at distances corresponding to the incremental recess distance of said stepping bar, said collar is supported on said cage and said coupling means is operatively cooperative with said recesses to longitudinally couple said collar to said expander.
 8. Tube expander apparatus according to claim 6 including stepping means operable in controlled sequence by said control means to displace said latch means in a first direction relative to said stepping bar when the latch means is in a release relation therewith and to displace said latch means together with said stepping bar in an opposite direction when said latch means is in a latch relation therewith.
 9. Tube expander apparatus according to claim 8 in which said stepping means comprises a stepping cylinder operative concomitantly with said latch means.
 10. Tube expander apparatus according to claim 9 in which said control means is pneumatically actuated. 